Test Compaction Using (k, 1)-Cycle Tests

Compaction of scan-based test sets is important for reducing the test application time and test data volume. For a circuit with K flip-flops in its longest scan chain, a conventional single-cycle scan-based test starts with a scan-in operation of K scan shift cycles, followed by a single functional capture cycle. The test ends with a scan-out operation of K scan shift cycles that is overlapped with the scan-in operation of the next test. Such a test is referred to as a $(K, 1)$-cycle test. This article defines a $(k, 1)$-cycle test to have 0 ≤ k ≤ K scan shift cycles in its scan-in and scan-out operations. A $(k, 1)$-cycle test is compressed similar to a conventional $(K, 1)$-cycle test, and overlapping of scan-out and scan-in operations can be performed as for conventional tests. The advantage of using $(k, 1)$-cycle tests with 0 ≤ k< K is that they require fewer clock cycles, thus contributing to test compaction by reducing the number of clock cycles required for test application. This article describes a test generation procedure that produces a compressed test set based on the use of $(k, 1)$ cycle tests. Experimental results for single stuck-at faults in benchmark circuits demonstrate the effectiveness of $(k, 1)$-cycle tests for test compaction.